Brobo

>>there must be max downhaul to get the shape that way,....

Downhaul AND bending away of the mast top.
It appears the top of the masts are bending away to leeward. Intended wingmast behaviour. This depowers a boat like nobodies business.

>>they are depowering the top 1/3rd of the sailplan to keep the Uni in balance upwind......not very efficient, don't you think?

It also tends to hurt pointing.

>>does the 18HT rule allow for a sail smaller than maximum s.a.?.....or is one committed to use max s.a. in all conditions?

Smaller is allowed. I don't remember wether you would have to use the same suit of sails for the whole event.

Wouter